649 research outputs found
High-Energy Approach for Heavy-Ion Scattering with Excitations of Nuclear Collective States
A phenomenological optical potential is generalized to include the Coulomb
and nuclear interactions caused by the dynamical deformation of its surface. In
the high-energy approach analytical expressions for elastic and inelastic
scattering amplitudes are obtained where all the orders in the deformation
parameters are included. The multistep effect of the 2 rotational state
excitation on elastic scattering is analyzed. Calculations of inelastic cross
sections for the O ions scattered on different nuclei at about hundred
Mev/nucleon are compared with experimental data, and important role of the
Coulomb excitation is established.Comment: 9 pages; 3 figures. Submitted to the Physics of Atomic Nucle
`Composite particles' and the eigenstates of Calogero-Sutherland and Ruijsenaars-Schneider
We establish a one-to-one correspondance between the ''composite particles''
with particles and the Young tableaux with at most rows. We apply this
correspondance to the models of Calogero-Sutherland and Ruijsenaars-Schneider
and we obtain a momentum space representation of the ''composite particles'' in
terms of creation operators attached to the Young tableaux. Using the technique
of bosonisation, we obtain a position space representation of the ''composite
particles'' in terms of products of vertex operators. In the special case where
the ''composite particles'' are bosons and if we add one extra quasiparticle or
quasihole, we construct the ground state wave functions corresponding to the
Jain series of the fractional quantum Hall effect.Comment: latex calcomp2.tex, 5 files, 30 pages [SPhT-T99/080], submitted to J.
Math. Phy
Study of He+C Elastic Scattering Using a Microscopic Optical Potential
The He+C elastic scattering data at beam energies of 3, 38.3 and
41.6 MeV/nucleon are studied utilizing the microscopic optical potentials
obtained by a double-folding procedure and also by using those inherent in the
high-energy approximation. The calculated optical potentials are based on the
neutron and proton density distributions of colliding nuclei established in an
appropriate model for He and obtained from the electron scattering form
factors for C. The depths of the real and imaginary parts of the
microscopic optical potentials are considered as fitting parameters. At low
energy the volume optical potentials reproduce sufficiently well the
experimental data. At higher energies, generally, additional surface terms
having form of a derivative of the imaginary part of the microscopic optical
potential are needed. The problem of ambiguity of adjusted optical potentials
is resolved requiring the respective volume integrals to obey the determined
dependence on the collision energy. Estimations of the Pauli blocking effects
on the optical potentials and cross sections are also given and discussed.
Conclusions on the role of the aforesaid effects and on the mechanism of the
considered processes are made.Comment: 12 pages, 9 figures, accepted for publication in Physical Review
Charge and matter distributions and form factors of light, medium and heavy neutron-rich nuclei
Results of charge form factors calculations for several unstable neutron-rich
isotopes of light, medium and heavy nuclei (He, Li, Ni, Kr, Sn) are presented
and compared to those of stable isotopes in the same isotopic chain. For the
lighter isotopes (He and Li) the proton and neutron densities are obtained
within a microscopic large-scale shell-model, while for heavier ones Ni, Kr and
Sn the densities are calculated in deformed self-consistent mean-field Skyrme
HF+BCS method. We also compare proton densities to matter densities together
with their rms radii and diffuseness parameter values. Whenever possible
comparison of form factors, densities and rms radii with available experimental
data is also performed. Calculations of form factors are carried out both in
plane wave Born approximation (PWBA) and in distorted wave Born approximation
(DWBA). These form factors are suggested as predictions for the future
experiments on the electron-radioactive beam colliders where the effect of the
neutron halo or skin on the proton distributions in exotic nuclei is planned to
be studied and thereby the various theoretical models of exotic nuclei will be
tested.Comment: 26 pages, 11 figures, 3 tables, accepted for publication in Phys.
Rev.
Calculations of He+p Elastic Cross Sections Using Microscopic Optical Potential
An approach to calculate microscopic optical potential (OP) with the real
part obtained by a folding procedure and with the imaginary part inherent in
the high-energy approximation (HEA) is applied to study the He+p elastic
scattering data at energies of tens of MeV/nucleon (MeV/N). The neutron and
proton density distributions obtained in different models for He are
utilized in the calculations of the differential cross sections. The role of
the spin-orbit potential is studied. Comparison of the calculations with the
available experimental data on the elastic scattering differential cross
sections at beam energies of 15.7, 26.25, 32, 66 and 73 MeV/N is performed. The
problem of the ambiguities of the depths of each component of the optical
potential is considered by means of the imposed physical criterion related to
the known behavior of the volume integrals as functions of the incident energy.
It is shown also that the role of the surface absorption is rather important,
in particular for the lowest incident energies (e.g., 15.7 and 26.25
MeV/nucleon).Comment: 11 pages, 7 figures, accepted for publication in Physical Review
Dynamical structure factor of the anisotropic Heisenberg chain in a transverse field
We consider the anisotropic Heisenberg spin-1/2 chain in a transverse
magnetic field at zero temperature. We first determine all components of the
dynamical structure factor by combining exact results with a mean-field
approximation recently proposed by Dmitriev {\it et al}., JETP 95, 538 (2002).
We then turn to the small anisotropy limit, in which we use field theory
methods to obtain exact results. We discuss the relevance of our results to
Neutron scattering experiments on the 1D Heisenberg chain compound .Comment: 13 pages, 14 figure
Quantum criticalities in a two-leg antiferromagnetic S=1/2 ladder induced by a staggered magnetic field
We study a two-leg antiferromagnetic spin-1/2 ladder in the presence of a
staggered magnetic field. We consider two parameter regimes: strong (weak)
coupling along the legs and weak (strong) coupling along the rungs. In both
cases, the staggered field drives the Haldane spin-liquid phase of the ladder
towards a Gaussian quantum criticality. In a generalized spin ladder with a
non-Haldane, spontaneously dimerized phase, the staggered magnetic field
induces an Ising quantum critical regime. In the vicinity of the critical
lines, we derive low-energy effective field theories and use these descriptions
to determine the dynamical response functions, the staggered spin
susceptibility and the string order parameter.Comment: 29 pages of revtex, 10 figure
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